Sudden hearing loss is one of the most disconcerting events in the lives of patients and audiology practices.  As its name suggests, there is no warning nor is there any way to predict who is as risk.  Typically, the audiologist meets the patient for the first time as the result of this sudden, potentially devastating event.  There is no time to get to know one another.  

The patient is terrified, probably has little if any knowledge of audiology, and enters the relationship is a decidedly defensive position.  Unlike typical counseling and consultative selling that accompanies acquired hearing loss, the audiologist’s professional response in the case of sudden loss must be at once highly diagnostic, highly supportive, and immediate.

 

What to Do

 

In every case, a person who experiences sudden hearing loss needs to be seen by both an audiologist and an Ear-Nose-Throat (otolaryngologist) physician, preferably one who specializes in ears (otologist). Audiometric evaluation should be performed immediately, though the audiologist needs to exercise care in selecting which tests to perform from the standard battery, avoiding those that introduce extreme pressure (atmospheric and sound) into the ear canal.  

The purpose of the hearing evaluation is two-fold: to measure how much hearing has been lost initially, and determine whether the sudden loss is due to malfunction of the hearing nerve or the middle ear.  Hearing losses due to nerve damage are called “sensorineural;” those due to middle ear problems are “conductive.” Sudden sensorineural hearing loss (SSNHL) is a medical emergency.

As soon as the hearing loss is charted, the patient goes into the hands of the physician for assessment and a treatment plan.  It is very important that serial audiograms are performed during the treatment and afterward, to determine whether recovery is present; also to determine whether post-medical treatment with amplification is in order, at which point the patient is handed back into the hands of the audiologist.

 It is not possible to predict recovery time or degree of recovery.  This is a time of great uncertainty for the patient as s/he waits and is handed back and forth between professions.

 

What Can Happen

 

In the past, different physicians and audiologists have used individualized approaches that depended on their experience, knowledge, and empathy.  Not every audiologist has had much if any experience with sudden hearing loss. A provider with little or no exposure to SSNHL is not a good thing for the patient who experiences this traumatic event.  

Alternatively, patients may end up in emergency rooms if this frightening event happens at a time which does not allow them quick access to hearing and ear specialists.  ER physicians are not going to approach the problem by ordering an audiogram, if for no other reason than that audiologists are not part of the ER experience.

All of the above spells out why there is a need for standardization of protocols for handling patients who present with sudden hearing loss.  In 2012, the American Academy of Otolaryngology published a Clinical Practice Guideline for Sudden Hearing Loss as a journal supplement.  It is summarized here:

KEY POINTS IN THE GUIDELINE

Among the main recommendations in the guideline are:

Prompt and accurate diagnosis is important:

  • Sensorineural (nerve) hearing loss should be distinguished clinically from conductive (mechanical) hearing loss.
  • The diagnosis of idiopathic sudden sensorineural hearing loss (ISSNHL) is made when audiometry confirms a 30-dB hearing loss at three consecutive frequencies and no underlying condition can be identified by history or physical exam.

Unnecessary tests and treatments should be avoided:

  • Routine head/brain CT scans, often ordered in the ER setting, are not helpful and expose the patient to ionizing radiation.
  • Routine, non-targeted, laboratory testing is not recommended.

Initial therapy for ISSNHL may include corticosteroids.

Follow-up and counseling is important:

  • 
Physicians should educate patients with ISSNHL about the natural history of the condition, the benefits and risks of medical interventions, and the limitations of existing evidence regarding efficacy.
  • Physicians should obtain follow-up audiometry within six months of diagnosis for patients with ISSNHL.
  • Physicians should counsel patients with incomplete hearing recovery about the possible benefits of amplification and hearing assistive technology and other supportive measures.

 Starting in 2010 Dr Frank Lin and colleagues commenced publishing results of studies of hearing loss and dementia, arriving at essentially the same conclusions using two paradigms and two different, large subject cohorts.  At the time, a Huffington Post article provided a good summary for lay readers of two studies loosely referred to as The Johns Hopkins Study and The Health ABC Study Hearing Cohort Study.  

Here is a summary of the Johns Hopkins Study (references below) for audiologists, who are encouraged to read it in full. It forms a bedrock for subsequent and ongoing studies  by the Lin group at Johns Hopkins. 

 

Hearing Loss & Dementia: The Johns Hopkins Study

 

The objective was “To determine whether hearing loss is associated with incident all-cause dementia and Alzheimer disease (AD). ”  The way the authors stated it is important to bear in mind:  not all dementia is due to Alzheimer’s.

 

Design

 

A total of 639 subjects, aged 36 to 90 years, were culled from the Baltimore Longitudinal Study on Aging (BLSA), a prospective NIH study ongoing since 1958.  All participated in hearing and cognitive tests in the study during the 1990-1994 time frame; none showed signs of dementia by test or observation when they were selected (see flow chart in Fig 1 from the published article).

The subjects were followed for over a decade (median = 11.9 years).  Besides hearing and cognitive status, the study measured and controlled for other variables that could influence cognition or hearing and confound results:  diabetes, blood pressure, blood pressure medication, sex, race, education, smoking, and hearing aid use.  The latter two variables were not measured directly but were based on subjects’ self reports.  Also, and importantly, hearing aid self report data was missing for 72 of the subjects.

 

Results

 

By the end of the study, over 9% (58/639) of the participants had some form of dementia (“all cause”).  Alzheimer’s was present in 5.8% of the total group (37/639), accounting for 63.8% of all dementias  37/58).

The majority of subjects (455/639) had normal hearing at the beginning of the study.  Most of the 184 subjects with hearing loss were males (135).  They were also older, on average, and more likely to have high blood pressure.  The question was, were those with hearing loss at the start of the study more likely to develop dementias over the study’s span, compared to their normal-hearing counterparts, and  independent of other variables?

Although some of those with normal hearing undoubtedly developed hearing loss during the 11+ year study, hearing status was not rechecked at the end of the study, so the question does not ask whether increasing hearing loss over time is associated with changes in cognition or changes in the covariables.

Here’s what the researchers found:

  • Dementia was linked to age, hypertension and hearing loss.  It was also linked to hearing aid use (which does not mean that hearing aids cause dementia).
  • Participants with hearing loss were more at risk (greater hazard, see fig 2)  than those without hearing loss to develop dementia, independent of the other variables.
  • For those >60 years old, more than 1/3 of the risk of dementia was independently associated with hearing loss.
  • The greater the hearing loss, the higher the likelihood of developing dementia.
  • Specifically, risk of dementia increased by about 20% for every additional 10 dB of hearing loss.
  • The 20% risk increase per 10 dB of hearing loss was the same for Alzheimer’s disease as it was for dementias in general.

 

What Do These Findings Mean?

 

First, they do not form a causal link between hearing loss and dementia:  we don’t know whether hearing loss causes dementia or vice versa, or neither causes the other.  We just know that they are likely to be linked in at least 1/3 of those who develop dementia.  As always, correlation is not causation.

Regression statistics are tricky. The way to interpret Figure 2 is that among those who were identified as having hearing loss, the “hazard ratio” of developing dementia was greater than the rest of the group, and likelihood increased (coefficient of 1.20) with increasing amounts of hearing loss at the outset. That is what is shown in Figure 2 by the rising solid line.

As you can tell from the numbers in the cohort, most with hearing loss did NOT develop dementia, regardless of degree of hearing loss at the outset, but the incidence was statistically higher for HL group than overall group.

We also don’t have much if any basis to connect use or non-use of hearing aids to risk of dementia.  The data were sparse and based on self report.  The  authors pointed to this as a weakness of the study but they weren’t really studying corrected hearing loss anyway.  It’s was not as much a weakness as it was a spur for future research.

 

 

References & Footnotes

 

Lin FR et al.  Hearing Loss and Incident Dementia. Arch Neurol. 2011;68(2):214-220. doi:10.1001/archneurol.2010.362.

Lin FR et al. Hearing Loss and Cognitive Decline in Older Adults. JAMA Intern Med. 2013;173(4):293-299. doi:10.1001/jamainternmed.2013.1868.